No. It turns out not so bad. My host machine is a desktop with 8GB RAM, 7200RPM Western Digital WD1002FBYS. The CPU is four core Q6600 (2.66GHz). I granted 4 GB RAM to the virtual machine, and it works OK . After rebooting the SQL Server and IIS, it took around 1 minute to load the first page. After that, it's as quick as SharePoint 2010.

Possibly the only tip is about SQL Server RAM configuration. I put 1GB limit to it. (For SharePoint 2010, I usually give it 500MB).

Update (24/07/2012):

I noticed that there was a process took quite a lot of memory:

Obviously, if the development environment doesn't have enough RAM, it doesn't make sense to run a "memory caching" service which consumes more than 600MB memory. So we can disable it through SharePoint Service Management page: